Thursday, 22 April 2021

Deep Sea Volcanoes - What Do We Know - Not Much

Deep Sea Volcanoes - What Do We Know - Not Much

A correspondent and I both spotted THIS ARTICLE today, and we both thought it was worth putting on the blog.

Most of the Earth's volcanic activity occurs under the sea but this was not realised until the 1950's and even today very little is known about it - mid-ocean ridges and black smokers. 

It was thought that deep-sea eruptions were rather boring. In particular explosive eruptions would not happen as the water pressure would prevent the possibility of steam. But now the presence of tephra tells us that explosive eruptions do occur - caused by expanding bubbles of carbon dioxide.

Megaplumes of hydrothermal fluids in the ocean have been detected, up to and over 100 cubic kilometres in volume. This is a lot of Olympic sized swimming pools!

Mapping of volcanic ash deposits suggests that the ash dispersal is caused by high energy plumes. The amounts of energy required are huge and the plumes form quickly over seafloor eruptions and are formed, not from the energy of a lava flow - these would be too small - but by the expulsion of hot fluids (hotter than 300℃) from the sea bed. The eruption of the lava drives the expulsion of a much larger volume of  hydrothermal fluid.

The Dispersal of Early Life

The authors propose that a side effect of these plumes is the dispersal of life across the Earth. And as life may have started in the extremophile communities, they may have been an influence on the origin of life on Earth.

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